Why did Justin Trudeau support Bill C-51 despite criticizing it?

Justin Trudeau’s support for Bill C-51 in 2015, despite his stated opposition to the legislation, was a strategic political decision. While Trudeau publicly expressed that he opposed the bill, he ultimately voted in favor of it to prevent the Conservative government, led by Prime Minister Stephen Harper, from using a "no" vote against him for political gain in the upcoming general election.1

The legislation, which aimed to strengthen antiterrorism measures and expand the surveillance powers of the Canadian Security Intelligence Service (CSIS), was highly controversial. Critics, including the New Democratic Party, argued that the bill violated civil liberties and lacked sufficient parliamentary oversight. By voting for the bill, Trudeau sought to neutralize the potential for the Conservatives to portray him as being soft on national security, a move that reflected the intense political pressure surrounding the 2015 federal election campaign.213